Get the external IP address from a Linux box

Hello,
I am looking for a native package on Debian, that can give me the
external IP address of the machine.
So far, I used internet sites, but I am sure there is a package that do
that properly, especially if one site is unreachable.
Something I can run from the command line, and that would return the
external IP address.
Thanks.
--
André Rodier
Homebox: https://github.com/progmaticltd/homebox